Hydraulic pressure supply system of automatic transmission

ABSTRACT

A hydraulic pressure supply system supplies hydraulic pressure generated at a hydraulic pump having two pump chambers to a low pressure portion and a high pressure portion and performs mode conversion from a full discharge mode to a two circuit mode or a half discharge mode according to variable control pressure of a solenoid valve.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to Korean Patent Application No.10-2013-0112194 filed on Sep. 17, 2013, the entire contents of which isincorporated herein for all purposes by this reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a hydraulic pressure supply system ofan automatic transmission. More particularly, the present inventionrelates to a hydraulic pressure supply system of an automatictransmission for a vehicle which changes its mode from full dischargemode to two circuit mode or half discharge mode according to variablecontrol pressure of a solenoid valve.

2. Description of Related Art

A gear pump is mainly used as a hydraulic pump applied to a hydraulicpressure supply system of an automatic transmission for a vehicle.However, a vane pump that can supply sufficient oil at a low speedregion is recently used.

The vane pump increases discharge amount in proportion to a rotationspeed thereof. If the vane pump is controlled to supply the sufficientoil at the low speed region, unnecessarily much oil is supplied andthereby causes driving loss of the pump at a high speed region.

Therefore, the vane pump includes first and second pump chambersdisposed on a shaft of a rotor so as to recirculate surplus oil at thehigh speed region.

The first pump chamber is a main pump chamber, and hydraulic pressuregenerated at the first pump chamber is supplied to a high pressureportion (friction members, pulleys and so on).

In addition, the second pump chamber is a sub pump chamber, andhydraulic pressure generated at the second pump chamber is suppliedselectively to the high pressure portion (friction members, pulleys andso on) or a low pressure portion (torque converter, cooling device,lubrication device and so on), or is recirculated.

In further detail, the hydraulic pressure generated at the first pumpchamber and the second pump chamber is supplied to the high pressureportion if an engine speed is low, but the hydraulic pressure generatedat the second pump chamber is recirculated to an inlet side if theengine speed is high. Therefore, driving loss of the pump may beminimized and fuel economy may be enhanced.

The information disclosed in this Background of the Invention section isonly for enhancement of understanding of the general background of theinvention and should not be taken as an acknowledgement or any form ofsuggestion that this information forms the prior art already known to aperson skilled in the art.

BRIEF SUMMARY

Various aspects of the present invention are directed to providing ahydraulic pressure supply system of an automatic transmission for avehicle having advantages of supplying hydraulic pressure generated at ahydraulic pump having two pump chambers to a low pressure portion and ahigh pressure portion and performing mode conversion from a fulldischarge mode to a two circuit mode or a half discharge mode accordingto variable control pressure of a solenoid valve.

In an aspect of the present invention, a hydraulic pressure supplysystem of an automatic transmission for a vehicle, may include ahydraulic pump provided with first and second pump chambers formedtherein, wherein the first and second pump chambers are connected to anoil pan respectively through first and second input lines and dischargegenerated hydraulic pressure respectively through first and seconddischarge lines, a high-pressure regulator valve disposed on ahigh-pressure line connected to the first discharge line and a highpressure portion, regulating hydraulic pressure supplied from the firstand second pump chambers to the high pressure portion though thehigh-pressure line to stable hydraulic pressure, and supplying surplushydraulic pressure to a low pressure portion through a firstrecirculation line connected to the high-pressure regulator valve, afirst switch valve connecting the second discharge line connected to thesecond pump chamber selectively to a first bypass line connected to thehigh-pressure line or a first low-pressure line, and controlled byvariable control pressure of a solenoid valve so as to supply thehydraulic pressure generated at the second pump chamber selectively tothe high-pressure line or the first low-pressure line, a second switchvalve connecting the first low-pressure line selectively to a secondbypass line connected to the first input line connected to the firstpump chamber or a second low-pressure line, and controlled by thevariable control pressure of the solenoid valve so as to recirculatehydraulic pressure supplied through the first low-pressure line to thefirst input line connected to the first pump chamber or supply thehydraulic pressure supplied through the first low-pressure line to thesecond low-pressure line, and a low-pressure regulator valve selectivelyconnecting the second low-pressure line to a third low-pressure lineconnected to the low pressure portion, regulating hydraulic pressuresupplied to the low pressure portion through the second low-pressureline and the third low-pressure line to stable hydraulic pressure, andrecirculating the surplus hydraulic pressure to the first input lineconnected to the first input line through a second recirculation lineconnected to the second bypass line.

The first switch valve is controlled by the variable control pressure ofa solenoid valve and elastic force of an elastic member counteractingagainst the variable control pressure.

The second switch valve is controlled by variable control pressure of asecond solenoid valve and elastic force of an elastic membercounteracting against the variable control pressure.

The variable control pressure may include first control pressureoperating only the first switch valve and second control pressure higherthan the first control pressure and operating both of the first andsecond switch valves.

The first recirculation line is connected between the high-pressureregulator valve and the third low-pressure line.

In another aspect of the present invention, a hydraulic pressure supplysystem of an automatic transmission for a vehicle, may include ahydraulic pump provided with first and second pump chambers formedtherein, wherein the first and second pump chambers are connected to anoil pan respectively through first and second input lines and dischargegenerated hydraulic pressure respectively through first and seconddischarge lines, a high-pressure regulator valve disposed on ahigh-pressure line connected to the first discharge line and a highpressure portion, controlled by control pressure of a first solenoidvalve so as to regulate the hydraulic pressure supplied from the firstand second pump chambers to the high pressure portion through thehigh-pressure line to be stable, and supplying surplus hydraulicpressure to a low pressure portion through a first recirculation lineconnected to the high-pressure regulator valve, a first switch valveconnecting the second discharge line selectively to a first bypass lineconnected to the high-pressure line or a first low-pressure line, andcontrolled by variable control pressure of a second solenoid valve so asto supply the hydraulic pressure generated at the second pump chamberselectively to the high-pressure line or the first low-pressure line, asecond switch valve connecting the first low-pressure line selectivelyto a second bypass line connected to the first input line or a secondlow-pressure line, and controlled by the variable control pressure ofthe second solenoid valve so as to recirculate the hydraulic pressuresupplied through the first low-pressure line to the first input line orsupply the hydraulic pressure supplied through the first low-pressureline to the second low-pressure line selectively, and a low-pressureregulator valve selectively connecting the second low-pressure line to athird low-pressure line connected to the low pressure portion,regulating the hydraulic pressure supplied to the low pressure portionthrough the third low-pressure line to be stable, and recirculatingsurplus hydraulic pressure to the first input line through a secondrecirculation line connected to the second bypass line.

The first switch valve is controlled by the variable control pressure ofthe second solenoid valve and elastic force of an elastic membercounteracting against the variable control pressure.

The second switch valve is controlled by the variable control pressureof the second solenoid valve and elastic force of an elastic membercounteracting against the variable control pressure.

The variable control pressure may include first control pressureoperating only the first switch valve and second control pressure higherthan the first control pressure and operating both of the first andsecond switch valves.

The first recirculation line is connected between the high-pressureregulator valve and the third low-pressure line.

The methods and apparatuses of the present invention have other featuresand advantages which will be apparent from or are set forth in moredetail in the accompanying drawings, which are incorporated herein, andthe following Detailed Description, which together serve to explaincertain principles of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a hydraulic pressure supply systemaccording to an exemplary embodiment of the present invention andillustrates oil flow at a full discharge mode.

FIG. 2 is a schematic diagram of a hydraulic pressure supply systemaccording to an exemplary embodiment of the present invention andillustrates oil flow at a two circuit mode.

FIG. 3 is a schematic diagram of a hydraulic pressure supply systemaccording to an exemplary embodiment of the present invention andillustrates oil flow at a half discharge mode.

It should be understood that the appended drawings are not necessarilyto scale, presenting a somewhat simplified representation of variousfeatures illustrative of the basic principles of the invention. Thespecific design features of the present invention as disclosed herein,including, for example, specific dimensions, orientations, locations,and shapes will be determined in part by the particular intendedapplication and use environment.

In the figures, reference numbers refer to the same or equivalent partsof the present invention throughout the several figures of the drawing.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments of thepresent invention(s), examples of which are illustrated in theaccompanying drawings and described below. While the invention(s) willbe described in conjunction with exemplary embodiments, it will beunderstood that the present description is not intended to limit theinvention(s) to those exemplary embodiments. On the contrary, theinvention(s) is/are intended to cover not only the exemplaryembodiments, but also various alternatives, modifications, equivalentsand other embodiments, which may be included within the spirit and scopeof the invention as defined by the appended claims.

An exemplary embodiment of the present invention will hereinafter bedescribed in detail with reference to the accompanying drawings.

Description of components that are not necessary for explaining thepresent exemplary embodiment will be omitted, and the same constituentelements are denoted by the same reference numerals in thisspecification.

In the detailed description, ordinal numbers are used for distinguishingconstituent elements having the same terms, and have no specificmeanings.

FIG. 1 is a schematic diagram of a hydraulic pressure supply systemaccording to an exemplary embodiment of the present invention andillustrates oil flow at a full discharge mode.

Referring to FIG. 1, a hydraulic pressure supply system according to anexemplary embodiment of the present invention includes a low pressureportion LP and a high pressure portion HP. Therefore, hydraulic pressuregenerated at a hydraulic pump OP is supplied simultaneously to the lowpressure portion LP and the high pressure portion HP or only to the highpressure portion HP.

The low pressure portion LP represents a portion to which a low pressurefacilitating operation of the torque converter (T/C) and cooling andlubrication is supplied, and the high pressure portion HP represents aportion to which a high pressure facilitating operation of a pluralityof friction members that is selectively operated when shifting or apulley (e.g., pulley for a CVT) is supplied.

The hydraulic pressure supply system according to the exemplaryembodiment of the present invention including the low pressure portionLP and the high pressure portion HP includes a hydraulic pump OP, ahigh-pressure regulator valve RV1, first and second switch valves SV1and SV2, and a low-pressure regulator valve RV2.

The hydraulic pump OP is a vane pump and includes first and second pumpchambers 11 and 12 formed therein. The first and second pump chambers 11and 12 receive oil in an oil pan P respectively through first and secondinput lines 13 and 14, and hydraulic pressure generated at the first andsecond pump chambers 11 and 12 is supplied to the high pressure portionHP and the low pressure portion LP respectively through first and seconddischarge lines 15 and 16.

The high-pressure regulator valve RV1 is disposed on the high-pressureline 21 connected to the high pressure portion HP, regulates thehydraulic pressure supplied from the first and second pump chambers 11and 12 to the high pressure portion HP through the high-pressure line 21to stable hydraulic pressure, and supplies surplus hydraulic pressure tothe low pressure portion LP through a first recirculation line 41.

The first switch valve SV1 connects the second discharge line 16selectively to a first bypass line 61 connected to the high-pressureline 21 or to a first low-pressure line 31. Therefore, the first switchvalve SV1 supplies the hydraulic pressure generated at the second pumpchamber 12 selectively to the high-pressure line 21 or the firstlow-pressure line 31.

The second switch valve SV2 connects the first low-pressure line 31selectively to a second bypass line 62 connected to the first input line13 or to a second low-pressure line 32. Therefore, the second switchvalve SV2 recirculates the hydraulic pressure supplied through the firstlow-pressure line 31 to the first input line 13 or supplies thehydraulic pressure supplied through the first low-pressure line 31 tothe second low-pressure line 32 selectively.

The low-pressure regulator valve RV2 connects the second low-pressureline 32 to a third low-pressure line 33 connected to the low pressureportion LP, regulates the hydraulic pressure supplied to the lowpressure portion LP through the second low-pressure line 32 and thethird low-pressure line 33 to be stable, and recirculates surplushydraulic pressure to the first input line 13 through a second bypassline 62 connected to a second recirculation line 42.

The hydraulic pressure supply system according to the exemplaryembodiment of the present invention will be described in further detail.

The hydraulic pump OP is a vane pump and includes the first and secondpump chambers 11 and 12 formed therein. The first pump chamber 11 andthe second pump chamber 12 are formed symmetrically with respect to arotor 17 in an axial direction.

The first pump chamber 11 is connected to the first input port 11 a andthe first discharge port 11 b, and the second pump chamber 12 isconnected to the second input port 12 a and the second discharge port 12b.

The first and second input ports 11 a and 12 a are connected to the oilpan P respectively through the first and second input lines 13 and 14,and the first and second discharge ports 11 b and 12 b are connectedrespectively to the first and second discharge lines 15 and 16.

The first discharge line 15 is always connected to the high pressureportion HP through a high-pressure line 21, and the second dischargeline 16 is connected to the first switch valve SV1.

In addition, the high-pressure regulator valve RV1 is disposed on thehigh-pressure line 21. The high-pressure regulator valve RV1 iscontrolled by control pressure supplied from a first solenoid valve SOL1and elastic force of a first elastic member S1. The high-pressureregulator valve RV1 regulates the hydraulic pressure supplied to thehigh pressure portion HP to be stable and recirculates the surplushydraulic pressure at a regulating process to the low pressure portionLP through the first recirculation line 41.

That is, the first recirculation line 41 connects the high-pressureregulator valve RV1 with the third low-pressure line 33.

The first switch valve SV1 is connected to the second switch valve SV2through the first low-pressure line 31 and is connected to thehigh-pressure line 21 through the first bypass line 61.

The first switch valve SV1 is controlled by a second solenoid valveSOL2. That is, the first switch valve SV1 is controlled by variablecontrol pressure of the second solenoid valve and elastic force of asecond elastic member S2 counteracting the variable control pressure,and connects the second discharge line 16 selectively to the firstlow-pressure line 31 or the first bypass line 61.

In addition, the second switch valve SV2 is connected to the firstswitch valve SV1 through the first low-pressure line 31, is connected tothe low-pressure regulator valve RV2 through the second low-pressureline 32, and is connected to the first input line 13 through the secondbypass line 62.

The second switch valve SV2 is controlled by the second solenoid valveSOL2. That is, the second switch valve SV2 is controlled by the variablecontrol pressure of the second solenoid valve and elastic force of athird elastic member S3 counteracting against the variable controlpressure, and connects the first low-pressure line 31 selectively to thesecond low-pressure line 32 or the second bypass line 62.

Herein, the variable control pressure of the second solenoid valve SV2includes two control pressures (first and second control pressures)having different strength. The second control pressure may be higherthan the first control pressure. In addition, the first switch valve isoperated at pressure higher than the first control pressure, and thesecond switch valve is operated at pressure higher than the secondcontrol pressure.

That is, the elastic force of the second elastic member S2 provided inthe first switch valve SV1 is weaker than that of the third elasticmember S3 provided in the second switch valve SV2. Therefore, if thefirst control pressure is supplied from the second solenoid valve SOL2,the first switch valve SV1 is operated so as to switch hydraulic lines.In addition, if the second control pressure higher than the firstcontrol pressure is supplied, the second switch valve SV2 is operated soas to switch hydraulic lines.

The low-pressure regulator valve RV2 is connected to the second switchvalve SV2 through the second low-pressure line 32, is connected to thelow pressure portion LP through the third low-pressure line 33, and isconnected to the second bypass line 62 through the second recirculationline 42.

The low-pressure regulator valve RV2 is controlled by the hydraulicpressure supplied through the second low-pressure line 32 and elasticforce of a fourth elastic member S4. The low-pressure regulator valveRV2 regulates the hydraulic pressure supplied from the secondlow-pressure line 32 to be stable, and supplies the regulated hydraulicpressure to the low pressure portion LP through the third low-pressureline 33.

In addition, the surplus hydraulic pressure of the low pressure portionLP that is generated at a regulating process of the low-pressureregulator valve RV2 is recirculated to the first input line 13 throughthe second recirculation line 42 and the second bypass line 62.

The hydraulic pressure supply system according to the exemplaryembodiment of the present invention is controlled to be operated at thefull discharge mode at initial starting and when stopped.

Referring to FIG. 1, the first switch valve SV1 connects the seconddischarge line 16 to the first bypass line 61 at the full dischargemode.

Therefore, the hydraulic pressure generated at the first and second pumpchambers 11 and 12 of the hydraulic pump OP is entirely supplied to thehigh pressure portion HP through the first and second discharge lines 15and 16, and the surplus hydraulic pressure of the high-pressureregulator valve RV1 is supplied to the low pressure portion LP throughthe first recirculation line 41.

FIG. 2 is a schematic diagram of a hydraulic pressure supply systemaccording to an exemplary embodiment of the present invention andillustrates oil flow at a two circuit mode.

Referring to FIG. 2, if the hydraulic pressure supplied to the highpressure portion HP increases due to rise of an engine speed and drivingcondition during the vehicle runs at the full discharge mode, the twocircuit mode is achieved. At this time, the second solenoid valve SOL2supplies the first control pressure and only the first switch valve SV1is operated. That is, the first switch valve SV1 connects the seconddischarge line 16 with the first low-pressure line 31.

Therefore, the hydraulic pressure generated at the first pump chamber 11is supplied to the high pressure portion HP through the first dischargeline 15 and the high-pressure line 21, and the hydraulic pressuregenerated at the second pump chamber 12 is supplied to the low pressureportion LP through the first, second, and third low-pressure lines 31,32, and 33, the first and second switch valves SV1 and SV2, and thelow-pressure regulator valve RV2.

The hydraulic pressure generated at the first and second pump chambers11 and 12 of the hydraulic pump OP is supplied respectively to the highpressure portion HP and the low pressure portion LP through two circuitsat the two circuit mode. In addition, the surplus hydraulic pressure ofthe high pressure portion HP is additionally supplied to the lowpressure portion LP through the first recirculation line 41.

FIG. 3 is a schematic diagram of a hydraulic pressure supply systemaccording to an exemplary embodiment of the present invention andillustrates oil flow at a half discharge mode.

Referring to FIG. 3, if the second solenoid valve SOL2 supplies thesecond control pressure and both of the first and second switch valves14 and 16 are operated according to great rise of the engine speed andthe driving condition during the vehicle runs at the two circuit mode,the half discharge mode is achieved.

At this time, the first switch valve SV1 connects the second dischargeline 16 with the first low-pressure line 31, and the second switch valveSV2 connects the first low-pressure line 31 with the second bypass line62.

Therefore, the hydraulic pressure generated at the first pump chamber 11is supplied to the high pressure portion HP through the first dischargeline 15 and the high-pressure line 21, and the surplus hydraulicpressure of the high-pressure regulator valve RV1 is supplied to the lowpressure portion LP. In addition, the hydraulic pressure generated atthe second pump chamber 12 is recirculated to the first input line 13through the first and second low-pressure lines 31 and 32, the first andsecond switch valves SV1 and SV2, and the second bypass line 62.

That is, if the engine speed is high and engine torque is low, the halfdischarge mode is achieved. Since the hydraulic pressure generated atthe second pump chamber 12 of the hydraulic pump OP is recirculated toan input side of the hydraulic pump OP at the half discharge mode,driving torque of the hydraulic pump OP may be reduced, fuel economy maybe improved, and cavitation of the hydraulic pump OP when rotating withhigh speed may be prevented.

The hydraulic pressure supply system according to the exemplaryembodiment of the present invention may improve fuel economy bysupplying hydraulic pressure at an optimum mode according to the enginespeed and the driving condition of the vehicle.

That is, the hydraulic pressure generated at the first and second pumpchambers 11 and 12 of the hydraulic pump OP is entirely supplied to thehigh pressure portion HP through the high-pressure line 21, and thesurplus hydraulic pressure of the high-pressure regulator valve RV1 issupplied to the low pressure portion LP at the full discharge mode.

Since the hydraulic pressure generated at the hydraulic pump OP isentirely supplied to the high pressure portion HP at the full dischargemode, responsiveness to shifting may be enhanced and smooth start may besupported.

In addition, the hydraulic pressure generated at the first pump chamber11 of the hydraulic pump OP is supplied to the high pressure portion HPthrough the high-pressure line 21, and the hydraulic pressure generatedat the second pump chamber 12 is supplied to the low pressure portion LPthrough the first, second, and third low-pressure lines 31, 32, and 33,the first and second switch valves SV1 and SV2, and the low-pressureregulator valve RV2 at the two circuit mode.

Since oil amount of the low pressure portion LP increases and oil amountdemanded at the high pressure portion HP is reduced even though oilamount necessary for the transmission is supplied at the two circuitmode, the engine speed for entering the half discharge mode may belowered and fuel economy may be enhanced.

In addition, the hydraulic pressure generated at the first pump chamber11 of the hydraulic pump OP is supplied to the high pressure portion HPthrough the high-pressure line 21, and the hydraulic pressure generatedat the second pump chamber 12 is recirculated to the first input line 13through the first low-pressure line 31, the first and second switchvalves SV1 and SV2, and the second bypass line 62 at the half dischargemode.

Since the hydraulic pressure generated at the first pump chamber 11 issupplied to the high pressure portion HP, a portion of the hydraulicpressure is supplied to the low pressure portion LP, and the hydraulicpressure generated at the second pump chamber 12 is recirculated to thehydraulic pump OP at the half discharge mode, driving torque of thehydraulic pump OP may be reduced, fuel economy may be enhanced, andcavitation of the hydraulic pump OP may be prevented when rotating withhigh speed.

The hydraulic pressure supply system according to the exemplaryembodiment of the present invention can use the variable controlpressure of the solenoid valve when a mode is changed to the two circuitmode and the half discharge mode. Therefore, the hydraulic pressure maybe supplied at the optimum mode according to the engine speed and thedriving condition of the vehicle and fuel economy may be improved.

That is, since one solenoid valve (i.e., second solenoid valve SV2)generates two control pressures having different strength so as tocontrol the first and second switch valves SV1 and SV2, at least onesolenoid valve may be removed and manufacturing cost may be curtailed.

For convenience in explanation and accurate definition in the appendedclaims, the terms “upper”, “lower”, “inner” and “outer” are used todescribe features of the exemplary embodiments with reference to thepositions of such features as displayed in the figures.

The foregoing descriptions of specific exemplary embodiments of thepresent invention have been presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed, and obviously manymodifications and variations are possible in light of the aboveteachings. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed, and obviously manymodifications and variations are possible in light of the aboveteachings as well as various alternatives and modifications thereof. Itis intended that the scope of the invention be defined by the Claimsappended hereto and their equivalents.

What is claimed is:
 1. A hydraulic pressure supply system of anautomatic transmission for a vehicle, comprising: a hydraulic pumpprovided with first and second pump chambers formed therein, wherein thefirst and second pump chambers are connected to an oil pan respectivelythrough first and second input lines and discharge generated hydraulicpressure respectively through first and second discharge lines; ahigh-pressure regulator valve disposed on a high-pressure line connectedto the first discharge line and a high pressure portion, regulatinghydraulic pressure supplied from the first and second pump chambers tothe high pressure portion through the high-pressure line to stablehydraulic pressure, and supplying surplus hydraulic pressure to a lowpressure portion through a first recirculation line connected to thehigh-pressure regulator valve; a first switch valve connecting thesecond discharge line connected to the second pump chamber selectivelyto a first bypass line connected to the high-pressure line or a firstlow-pressure line, and controlled by variable control pressure of asolenoid valve so as to supply the hydraulic pressure generated at thesecond pump chamber selectively to the high-pressure line or the firstlow-pressure line; a second switch valve connecting the firstlow-pressure line selectively to a second bypass line connected to thefirst input line connected to the first pump chamber or a secondlow-pressure line, and controlled by the variable control pressure ofthe solenoid valve so as to recirculate hydraulic pressure suppliedthrough the first low-pressure line to the first input line connected tothe first pump chamber or supply the hydraulic pressure supplied throughthe first low-pressure line to the second low-pressure line; and alow-pressure regulator valve selectively connecting the secondlow-pressure line to a third low-pressure line connected to the lowpressure portion, regulating hydraulic pressure supplied to the lowpressure portion through the second low-pressure line and the thirdlow-pressure line to stable hydraulic pressure, and recirculating thesurplus hydraulic pressure to the first input line through a secondrecirculation line connected to the second bypass line.
 2. The hydraulicpressure supply system of claim 1, wherein the first switch valve iscontrolled by the variable control pressure of solenoid valve andelastic force of an elastic member counteracting against the variablecontrol pressure.
 3. The hydraulic pressure supply system of claim 1,wherein the second switch valve is controlled by variable controlpressure of the solenoid valve and elastic force of an elastic membercounteracting against the variable control pressure.
 4. The hydraulicpressure supply system of claim 1, wherein the variable control pressureincludes first control pressure operating only the first switch valveand second control pressure higher than the first control pressure andoperating both of the first and second switch valves.
 5. The hydraulicpressure supply system of claim 1, wherein the first recirculation lineis connected between the high-pressure regulator valve and the thirdlow-pressure line.
 6. A hydraulic pressure supply system of an automatictransmission for a vehicle, comprising: a hydraulic pump provided withfirst and second pump chambers formed therein, wherein the first andsecond pump chambers are connected to an oil pan respectively throughfirst and second input lines and discharge generated hydraulic pressurerespectively through first and second discharge lines; a high-pressureregulator valve disposed on a high-pressure line connected to the firstdischarge line and a high pressure portion, controlled by controlpressure of a first solenoid valve so as to regulate the hydraulicpressure supplied from the first and second pump chambers to the highpressure portion through the high-pressure line to be stable, andsupplying surplus hydraulic pressure to a low pressure portion through afirst recirculation line connected to the high-pressure regulator valve;a first switch valve connecting the second discharge line selectively toa first bypass line connected to the high-pressure line or a firstlow-pressure line, and controlled by variable control pressure of asecond solenoid valve so as to supply the hydraulic pressure generatedat the second pump chamber selectively to the high-pressure line or thefirst low-pressure line; a second switch valve connecting the firstlow-pressure line selectively to a second bypass line connected to thefirst input line or a second low-pressure line, and controlled by thevariable control pressure of the second solenoid valve so as torecirculate the hydraulic pressure supplied through the firstlow-pressure line to the first input line or supply the hydraulicpressure supplied through the first low-pressure line to the secondlow-pressure line selectively; and a low-pressure regulator valveselectively connecting the second low-pressure line to a thirdlow-pressure line connected to the low pressure portion, regulating thehydraulic pressure supplied to the low pressure portion through thethird low-pressure line to be stable, and recirculating surplushydraulic pressure to the first input line through a secondrecirculation line connected to the second bypass line.
 7. The hydraulicpressure supply system of claim 6, wherein the first switch valve iscontrolled by the variable control pressure of the second solenoid valveand elastic force of an elastic member counteracting against thevariable control pressure.
 8. The hydraulic pressure supply system ofclaim 6, wherein the second switch valve is controlled by the variablecontrol pressure of the second solenoid valve and elastic force of anelastic member counteracting against the variable control pressure. 9.The hydraulic pressure supply system of claim 6, wherein the variablecontrol pressure includes first control pressure operating only thefirst switch valve and second control pressure higher than the firstcontrol pressure and operating both of the first and second switchvalves.
 10. The hydraulic pressure supply system of claim 6, wherein thefirst recirculation line is connected between the high-pressureregulator valve and the third low-pressure line.